A botnet can be managed through which of the following?

IRC (Internet Relay Chat) has historically been the primary C&C mechanism for botnets because it allows a bot herder to join a private channel and broadcast commands to all infected hosts simultaneously. The protocol is lightweight, supports pseudonymous channels, and was widely available, making it ideal for coordinating large numbers of compromised machines. Most classic botnet families such as Agobot and SDBot used IRC-based C&C.

Email is not used for real-time botnet command issuance because it lacks the low-latency, bidirectional channel structure needed to efficiently control large numbers of bots.

Social media platforms like LinkedIn and Facebook can theoretically be abused for covert C&C but are not a standard or primary botnet management channel.

A vulnerable FTP server is an attack target or a data exfiltration staging point, not a mechanism for issuing real-time commands to botnet members.